Did they require a lot of rehab (roof, siding, foundation work, serious dry rot, water damage, etc.) or was it mostly cosmetic clean up? 

Supreme Court unanimously held that a county's retention of the excess value of a home in a tax sale violated the Takings Clause of the Fifth Amendment.

HML is one that holds themselves out as a lender IE advertises has a website in states that its required is state licensed and NMLS registered does not matter the source of their funds its about how the business is set up and marketed.A private money lender is simply that a private person that is NOT in the business of making loans they are simply using their IRA or some excess cash to loan to those they usually personally know or meet at RIA events.

As a first time landlord, I’m looking for some friendly advice to help get this apartment cleaned up and safe, without infringing on his privacy in excess.

They rent well the value dynamics are different thean dry front properties of course and the factors that @Wayne Brooks mention are important. 

I think the money has to dry up for this cycle to stop, OR we slowly (painfully?)

Seems overall, the demand has dried up.

Many of the low income folks I have rented to are pros at "working the system" and will bleed you dry.

I sold my Denton County properties as the costs (primarily property taxes) were getting excessive. 

How do I go about estimating the cost of all the lumber needed, roof material, dry wall, siding, flooring etc. any advice helps,thanks Pat